From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v2 10/16] KVM: MMU: fask check whether page is writable Date: Tue, 17 Apr 2012 10:41:41 +0300 Message-ID: <4F8D1EB5.2000302@redhat.com> References: <4F87FA69.5060106@linux.vnet.ibm.com> <4F87FC82.2050302@linux.vnet.ibm.com> <4F8AE64F.7080909@redhat.com> <4F8B9115.2030807@linux.vnet.ibm.com> <4F8BEE1B.8000704@redhat.com> <4F8BF265.7020405@linux.vnet.ibm.com> <4F8C06ED.6020805@redhat.com> <4F8CE9CF.6050506@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM To: Xiao Guangrong Return-path: In-Reply-To: <4F8CE9CF.6050506@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 04/17/2012 06:55 AM, Xiao Guangrong wrote: > On 04/16/2012 07:47 PM, Avi Kivity wrote: > > > On 04/16/2012 01:20 PM, Xiao Guangrong wrote: > >>>> > >>>> It is used to avoid the unnecessary overload > >>> > >>> It's overloading me :( > >>> > >> > >> > >> Sorry. > >> > > > > The trick is to send those in separate patchset so the maintainer > > doesn't notice. > > > > > Thanks for your suggestion, i will pay more attention on it in the > further. > > For this patch, what did you mean of "those"? You mean the whole > rmap.PTE_LIST_WP_BIT (fast check for shadow page table write protection > and host write protection) or just about host_page_write_protect > (for KSM only)? All of it. Let's start with just modifying sptes concurrently and only later add reading bits from rmap concurrently, if it proves necessary. > > If we do not have rmap.PTE_LIST_WP_BIT, there may have regression on > shadow mmu. > > Hmm, do i need implement rmap.PTE_LIST_WP_BIT, then fast page fault? Let's try to measure the effect without rmap.PTE_LIST_WP_BIT. Usually PTE chains for page tables are short so the effect would be small. Of course we can't tell about all guest. -- error compiling committee.c: too many arguments to function